Compositing/render question
To animate the puddle jumper coming through the stargate you could use a boolean modifier to hide it behind the event horizon.




Create a cylinder big enough to enclose the puddle jumper and place it behind the stargate.
Add a boolean modifier to the puddle jumper and select the previous cylinder as the object and set the operation to difference.





Disable the renderability of the cylinder so that it isn't seen when rendering, or you could give it a transparent texture.








Edit:
The easy way doesn't always work. As the boolean modifier doesn't always give a good result with some meshes, it can be better to do it in compositing. By giving the hideout mesh an object index you can use it to create a mask in the compositor. This answer explains using an object ID to composite multiple objects together.

First you want the background to be transparent, by enabling transparent in the film settings (part of the render settings).



Enable Object Index in the render layers.



Then give the object an index number.



Now in the compositor you can add an ID Mask node and connect that to the IndexOB and set the index number to match the number you set for the hideout object. The little box in the mix node will combine the alpha from the render and the mask.